A multiple input multiple output (MIMO) wireless communications system can obtain diversity and array gains by using a transmitted precoding technology and a receive combining technology. A system using precoding may be represented by:y=H{circumflex over (V)}s+n 
where y is a received signal vector, H is a channel matrix, {circumflex over (V)} is a precoding matrix, s is a transmitted symbol vector, and n is measured noise.
Optimal precoding usually requires channel state information (CSI) to be fully known to a transmitter. In a common method, a user equipment (UE) quantifies transient CSI and reports quantified transient CSI to a base station, where the user equipment includes a mobile station (MS), a relay (Relay), a mobile telephone (Mobile Telephone), a handset (handset), a portable device (portable equipment), and the like, and the base station includes a NodeB (NodeB) base station (Base Station, BS), an access point (Access Point), a transmission point (Transmission Point, TP), an evolved NodeB (Evolved NodeB, eNB), a relay (Relay), and the like. CSI information reported by an existing Long Term Evolution (Long Term Evolution, LTE) system includes information about a rank indicator (Rank Indicator, RI), a precoding matrix indicator (Precoding Matrix Indicator, PMI), a channel quality indicator (Channel Quality Indicator, CQI), and the like, in which the RI and the PMI indicate the number of transport layers and a precoding matrix that are used, respectively. A set of used precoding matrices is usually referred to as a codebook, in which each precoding matrix is a codeword in the codebook.
A codebook used in the existing LTE system is mainly designed for a single user multiple input multiple output (SU-MIMO) technology. When an existing codebook design is applied to a technology such as multi-user multiple input multiple output (MU-MIMO) or coordinated multi-point (CoMP), limitations of a capacity of a feedback channel and a size of a codebook set lower feedback precision, resulting in performance loss and a system throughput decrease.